Shazam.
1. I'm good with a gun.
Cassidy's primary skill is Small Guns. He is the best small gun NPC in the game.
2. However, getting up close might be even worse for you.
If you equip Cassidy with Power Armor or Advanced Power Armor before he's levelled up at least once, which can happen because NPCs levelling is random, his best skill becomes Melee Weapons.
3. Despite my occupation, I'm actually quite polite.
Cassidy is a bartender in the slum part of a post-apocalyptic city. However, if you play a female character, he mentions that the things Myron says aren't fit for a lady's ears.
4. I owe it all to clean living. Not straight-edge-clean-living, just the regular kind.
Cassidy can't use chems. If you use them ON him, he will die. However, he can use stims and drink booze just fine.
5. That's part of why I hate that pimply-faced kid so much.
Cassidy hates Myron. He frequently floats "Myron, you step outta line and I will cut you" when they're both in your group.
6. How that Super-Mutant can stand him, I have no idea.
Marcus often responds with "Don't worry, Myron. I'll protect you."